Cellular radiotelephones are commonly used to access many different types of systems, including voice mail and corporate information systems. Communications with these systems may often involve the entry of sensitive or proprietary information such as passwords from the keypad of the cellular radiotelephone.
Conventional radiotelephones typically display digits entered from the keypad as the keystrokes are performed. In addition, many conventional radiotelephones are able to recall previously entered digits. Because radiotelephones may often be operated in public places in which onlookers may view the radiotelephone's graphical display, or may be used by multiple parties, these features may lead to an unintended release of sensitive information.
Some conventional radiotelephones allow a user to manually clear display entries, as illustrated in FIG. 1. Referring to FIG. 1, a typical sequence for a call transaction (Block 100) may involve entering a number to dial (Block 110), pressing a send key (Block 120) and dialing the number (Block 130). After a communications session is established (Block 140), an additional transaction involving entry of sensitive information from the keypad may occur, e.g., entry of a personal identification number (PIN) (Block 150). After the communication session is ended by pressing an "END" key (Block 160) on the keypad, a "clear" (CLR) key on the keypad may be pressed (Block 170) to blank the display (Block 180).
In such a sequence, however, the PIN remains displayed until the call is terminated, allowing unauthorized onlookers to gain access to this sensitive information. In addition, should the user neglect to press the CLR key, others may gain access to the sensitive information.